Metathesis polytricyclononenes were synthesized via ROMP polymerization in the presence of the 1-st generation Grubbs catalyst and their gas-transport properties were studied for the first time. The aim of this work was to evaluate the influence of Me3E-groups (E = C, Si, Ge) on gas permeation parameters of ROMP materials. New metathesis poly(3-tert-butyltricyclononene-7) and poly(3-trimethylgermyltricyclononene-7) were obtained with high yields (up to 95%) and high-molecular weights (Mw∼3–7×105 g mol−1). The glass transition temperatures of the ROMP polytricyclononenes with Me3E-groups decreased when E was changed from C to Si and then to Ge. It was shown that the polytricyclononene containing Me3Si-groups has the highest gas permeability while the polytricyclononene containing Me3C-substituents has the lowest gas permeability. In addition, the gas permeation parameters were estimated for ROMP Me3Si- and Me3Ge-substituted polytricyclonona-3,7-dienes. So the influence of the second double bond in the monomer units on the permeability of the polymers obtained was studied. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 41395.